Gas turbine assembly for power plant comprising compact broadband damping device

Abstract

The invention relates to a gas turbine assembly for an electrical power plant comprising a compact broadband damping device, in particular to a gas turbine for an electrical power plant, the gas turbine having an axis and comprising: a compressor section for compressing ambient air; a combustor section for mixing and combusting the compressed air with at least one fuel; the combustor section comprising at least one liner defining a combustion chamber, the combustion chamber having an axial direction; at least one turbine section for expanding the hot gas stream leaving the combustion of the combustor and doing work on a rotor; at least one damping device arranged outside the combustion chamber and comprising a damping volume and a perforated plate, the perforated plate being configured to fluidically connect the combustion chamber to the damping volume for damping pressure fluctuations generated within the combustion chamber; wherein the perforated plate is inclined such that the radial thickness of the perforated plate varies along the axial combustor direction and / or along the circumferential combustor direction.

Description

[0001] Cross-reference to related applications

[0002] This patent application claims priority to European Patent Application No. 20197905.1, filed on September 3, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This invention relates to the technical field of gas turbine assemblies for power equipment. As is known, in a gas turbine assembly (hereinafter simply referred to as a gas turbine), an incoming airflow is compressed in a compressor, then mixed with fuel and ignited in a combustor to generate a hot gas flow that expands in the turbine to produce rotational work on a rotor, which is in turn connected to a generator. Combustion / flame instabilities occur within the combustor. These combustion / flame instabilities generate pressure fluctuations within the combustion chamber, which can cause mechanical damage to the combustor structure. In this technical field, the invention specifically relates to how to dampen a wide range of combustion pressure fluctuations with minimal impact on the available space outside the combustor. Background Technology

[0004] As is known, a gas turbine for electrical equipment (hereinafter referred to simply as a gas turbine) comprises a rotor having an upstream compressor section, a combustor section, and a downstream turbine section. The terms downstream and upstream refer to the direction of the main gas flow through the gas turbine. Specifically, the compressor comprises an inlet for supplied air and multiple blades for compressing the air passing through it. Compressed air leaving the compressor flows into the air chamber, i.e., a closed volume limited by the outer casing, and from there into the combustor. The compressed air is mixed with at least one fuel within the combustor. The fuel-compressed air mixture flows into the combustor, where it is burned. The resulting hot gas leaves the combustor and expands in the turbine, thereby doing work on the rotor.

[0005] High turbine inlet temperatures are required to achieve high efficiency. However, this high temperature results in high NOx emissions.

[0006] To reduce these emissions and increase operational flexibility, specific types of gas turbines that perform sequential combustion cycles are now known.

[0007] Typically, a sequential gas turbine comprises two combustors connected in series, with each combustion stage equipped with a burner and a combustion chamber. Along the direction of the main gas flow, the upstream combustor is called the "premixed" combustor and is supplied with compressed air. The downstream combustor is called the "sequential" or "reheat" combustor and is supplied with hot gas exiting the first combustion chamber. According to the first type of sequential gas turbine, the two combustors are physically separated by stages of turbine blades called a high-pressure turbine.

[0008] Along the main gas flow, this first type of sequential gas turbine includes a compressor, a first combustor, a high-pressure turbine, a second combustor, and a low-pressure turbine. The compressor and the two turbines may be connected to a common rotor that rotates about an axis and is surrounded by a concentric housing.

[0009] A second type of sequential gas turbine is known, in which the gas turbine does not have a high-pressure turbine, and the premixed and reheat combustors are arranged directly downstream of each other in a ring of canister combustors arranged around the turbine axis. Each canister combustor has a liner, i.e., a shell that restricts the internal combustion chamber, which is divided into two parts, upstream and downstream of the reheat burner, respectively. The upstream part of the liner is called the premixed liner, and the downstream part is called the sequential liner, and is connected downstream to a flange called a frame facing the turbine. Typically, the sequential liner and the frame are implemented as a single piece called a transition duct, which is configured to direct the hot gas leaving the combustor to the turbine, and in particular to the first stator vane of the turbine.

[0010] Of course, based on existing technical practices, it is possible to realize a canister burner with a single combustion stage, and thus include a single burner and a single liner defining a single combustion chamber.

[0011] Because the invention can be applied to all two different types of canister burners, the aforementioned different types of gas turbines are mentioned.

[0012] During operation, combustion / flame instabilities occur within the combustion chamber, generating pressure fluctuations. These pressure fluctuations can cause mechanical damage to the burner structure and limit operating procedures. Gas turbines typically must operate in lean combustion mode to meet emissions standards. During this operating mode, the burner flame convection disturbances are extremely sensitive and can easily couple with dynamic changes in the combustion chamber, leading to thermoacoustic instabilities.

[0013] Accordingly, it is now known to incorporate damping devices into the combustion chamber to dampen these pressure fluctuations. Conventional dampers consist of a damping volume fluidly connected to the combustion chamber, which acts as a resonator volume. Two different types of damping devices are known. The first type is called a Helmholtz damper and includes one or more small tubes called necks that connect the combustion chamber to the resonator volume. As is known, Helmholtz dampers are not very wideband. The damping can then be made widerband, pointing to more frequencies, by adding additional volumes and necks. Alternatively, multiple Helmholtz dampers tuned in parallel at another frequency can be provided, each connected to the combustion chamber. Multi-volume dampers can also be provided. From the first volume connected to the combustion chamber, a subsequent volume can be plugged in with another neck. Thus, the flow will enter the first volume, then the neck, then the second volume, and then through the second neck to the combustion chamber. Unfortunately, this type of damper has the disadvantage of having a large substantial impact on the available space outside the combustor (the “gas chamber”) where compressed air flows.

[0014] To achieve a more compact damping device, the second type of damper lacks the aforementioned neck but features a perforated plate, the inner surface of which is part of the combustion liner, i.e., in direct contact with hot gases. The outer surface of the perforated plate faces the resonator volume. This solution is indeed more compact than the Helmholtz damper.

[0015] Although perforated plate dampers have a wider bandwidth than single-volume Helmholtz dampers, the known damping device with a perforated plate connecting the combustion chamber to the resonator volume does not allow for damping a wide range of frequencies.

[0016] Based on this existing technology, there is now a need to improve the aforementioned damper with perforated plates in order to extend the frequency range of the damper with minimal impact on the available space outside the burner. Summary of the Invention

[0017] A primary objective of this invention is to provide an improved damping device for a gas turbine combustor. To achieve this objective, the present invention relates to a gas turbine for an electrical power unit, wherein the gas turbine has a shaft and includes:

[0018] - Compressor section used to compress ambient air.

[0019] - A burner section for mixing and burning compressed air with at least one fuel, wherein the burner section includes at least one liner defining a combustion chamber having an axial direction A and a circumferential burner direction C;

[0020] - At least one turbine section used to expand the hot gas stream leaving the burner and to do work on the rotor;

[0021] - At least one damping device disposed outside the combustion chamber and comprising a damping volume and a perforated plate, the perforated plate being configured to fluidly connect the combustion chamber to the damping volume to dampen pressure fluctuations generated within the combustion chamber.

[0022] The features listed above are well known to those skilled in the art, making further details unnecessary. As mentioned earlier, the combustor section can be implemented according to many different configurations. Preferably, the combustor section comprises a plurality of canister combustors arranged in a ring around the axis of the gas turbine.

[0023] According to a key aspect of the invention, the perforated plate is an inclined plate such that the radial extension or radial thickness of the perforated plate varies along the axial burner direction A and / or along the circumferential burner direction C.

[0024] The use of conventional perforated plate dampers (with a constant radial extension or thickness along the axial burner direction A or along the circumferential burner direction C) allows for broadband frequency dampers under certain functional mechanisms (at low Strouhal numbers (St < 0.5)). However, in the high-frequency range, it is difficult to remain at a low Strouhal mechanism, which is proportional to the target frequency. Furthermore, many frequencies fall outside the damping range, both in the low and high frequency ranges. As is known, in such dampers, the perforated plate thickness acts by changing the frequency of the damper's response. Advantageously, and preferably due to new additive / printing capabilities in the manufacturing process, it is anticipated according to the invention that perforated plates of different thicknesses can be printed for the same damping volume. This will thus provide a single damping volume (or rear cavity) closed by perforated plates equipped with channels having different radial extensions suitable for a wide frequency range of damping. This solution thus provides a large response over the frequency range with only one damping volume, minimizing the impact on the available space outside the burner.

[0025] The new perforated plate includes an inner surface, an outer surface, and a plurality of channels preferably extending radially from the inner surface to the outer surface. According to two alternative embodiments, the inner surface may be part of the burner liner, i.e., the inner surface directly faces the combustion chamber, or the inner surface may be connected to the outer surface used for the burner liner. In the latter case, at locations corresponding to the channels of the plate, the burner liner includes a plurality of holes for fluidly connecting the combustion chamber to the damping volume.

[0026] As mentioned above, the inner surface is flat and parallel to the axial burner direction, while the outer surface is inclined relative to the axial burner direction A and / or along the circumferential burner direction C, such that the radial extension of the channel varies along the axial burner direction A or along the circumferential burner direction C. According to different embodiments, the radial extension of the channel may decrease or increase along the hot gas flow direction M. Furthermore, the perforated plate may include a first portion and a second portion, in which the radial extension of the channel decreases along the axial burner direction in the first portion and increases along the axial burner direction A in the second portion.

[0027] Preferably, the damping volume discloses a constant radial extension along the axial burner direction A.

[0028] Alternatively or additionally, the radial extension may vary or remain constant along the circumferential burner direction C.

[0029] Preferably, the damping device includes a purge orifice for allowing purge air to enter the damping volume.

[0030] As mentioned above, the burner section preferably includes multiple canister burners. In this case, the damping device may be annular, forming a ring that circumferentially surrounds a portion of the canister burner liner.

[0031] More preferably, each of the aforementioned canister burners may be configured to perform two combustion stages in series and includes an upstream liner and a downstream liner. In this case, the damping device may be annular as a ring, circumferentially surrounding a portion of the downstream liner.

[0032] Preferably, the damping volume may include multiple sub-volumes, for example, in the case of annular structures, these sub-volumes are separated by multiple axially separating walls.

[0033] It should be understood that the foregoing general description and the following detailed description are exemplary and intended to provide a further explanation of the invention as claimed. Other advantages and features of the invention will become apparent from the following description, drawings, and claims.

[0034] The features of the invention, believed to be novel, are particularly claimed in the appended claims. Attached Figure Description

[0035] Further benefits and advantages of the invention will become apparent upon careful reading of the detailed description with appropriate reference to the accompanying drawings.

[0036] However, the invention itself can be best understood by referring to the following detailed description of the invention, which describes an exemplary embodiment of the invention, in conjunction with the accompanying drawings:

[0037] - Figure 1This is a schematic view of a gas turbine used in electrical equipment;

[0038] - Figure 2 This is a schematic view of a canister burner for a gas turbine used in electrical equipment, the canister burner having two combustion stages connected in series;

[0039] - Figure 3-5 This is a schematic view of a first embodiment of the damping device according to the present invention. Detailed Implementation

[0040] The technical content and details of the present invention are described below with reference to the accompanying drawings and preferred embodiments. These descriptions are not intended to limit the scope of the invention. Any equivalent variations and modifications made according to the appended claims are covered by the claims claimed in this invention.

[0041] Now for reference Figure 1 This is a schematic view of a gas turbine for power equipment, which may be equipped with the damping device of the present invention. In particular, Figure 1 A gas turbine 1 having an axis 9 and including a compressor 2, a combustion section 4, and a turbine 3 is disclosed. As is known, air 10 enters the compressor 2 and compressed air leaves the compressor 2 into a chamber 16, i.e., a volume defined by and surrounding the combustor by a housing 17. Compressed air 37 enters the combustor from the chamber 16; in this example, the combustor includes a plurality of canister-shaped combustors 4 arranged annularly around the axis 9. Figure 1 In the description, the terms annular, radial, axial, inner, and outer refer to axis 9, while the terms downstream and upstream refer to the main gas flow. Each canister burner 4 includes a burner 5 in which compressed air 37 is mixed with at least one fuel. This mixture is then burned in a combustion chamber 6, and the resulting hot gas flows downstream to turbine 3. Combustion chamber 6 is confined by a liner 7. Turbine 3 includes a plurality of stator blades 12 supported by stator carriers 14, and a plurality of rotor blades 13 supported by rotors 8. In turbine 3, the hot gas expands and does work on rotor 8, and exits turbine 3 as exhaust gas 11.

[0042] Now for reference Figure 2 This is an enlarged schematic view of a canister burner 4 that can be improved according to the present invention. Specifically, Figure 2A canister burner 4 with two-stage combustion in series and housed in associated port openings of a housing 17 is disclosed. The housing 17 defines a gas chamber 16 where compressed air is delivered by a compressor 2. The canister burner 4 has an axis 24 and includes, in series along the airflow direction M, a first burner or premixed burner 18 and a second burner or sequential burner 19. Specifically, the first burner 18 includes a first or premixed burner 20 and a first combustion chamber 21. The sequential burner 19 includes a sequential burner 22 and a second combustion chamber 23. The axis 24 is parallel to the airflow direction M. Figure 2 In one embodiment, fuel is supplied by a fuel gun 25 to a sequential burner 22, the fuel gun 25 extending axially outside the first combustion chamber 21 to the sequential burner 22. Combustion chambers 21 and 23 are bounded by a liner 7. Specifically, the premixed combustion chamber 21 is bounded by an upstream portion of the liner 7, while the sequential combustion chamber 21 is bounded by a sequential liner 26, which is part of a transition duct 27 for directing hot gas to the turbine. Figure 3 Similarly, in Figure 4 In the diagram, directions A, R, and C refer to the axial direction parallel to the main hot gas flow and the tank axis, the radial direction, and the circumferential or annular direction, respectively.

[0043] Now for reference Figure 3 This is a schematic view of an embodiment of the present invention. Specifically, Figure 3 It was made public that it could be done Figure 2 The combustion chamber of the first combustion chamber 21 or the second combustion chamber 23. Figure 3Reference numeral 28 refers to a damping device according to the invention. This damping device 28 includes a damping volume 29 (in the form of a cavity) disposed outside the combustion chamber and a perforated plate 30 connecting the combustion chamber to the damping volume 29. The perforated plate 30 includes an inner surface 31 and an outer surface 32, and a plurality of radial channels 33 extending from the inner surface 31 and the outer surface 32 for connecting the combustion chamber to the damping volume 29. The inner surface 31 may be integral with the lining of the combustion chamber, i.e., a single piece, or may be attached to the lining. In the latter case, the lining, of course, includes holes corresponding to the channels obtained in the perforated plate 30 to fluidly connect the combustion chamber to the damping volume 29. The outer surface 32 of the perforated plate 30 faces the damping volume 29. Those skilled in the art will understand how such a damping device (with a perforated plate) operates. According to the invention, the perforated plate 30 does not disclose a constant radial extension or a constant radial thickness, but is implemented as an "inclined" perforated plate, wherein the outer surface 32 is not parallel to the inner surface or burner liner, but is inclined relative to the axial direction. Therefore, the radial extension of the channel 33 obtained in the perforated plate 30 varies along the axial direction. In this example, the damping volume 29 discloses a constant radial extension along the axial direction to minimize the radial dimension of the damper, but it may also have different configurations. As is known, the damping volume 29 includes holes or openings / inlets for allowing purge air to enter the damping volume 29. In this example, the radial extension of the channel decreases along the axial direction A. However, different configurations are also possible, wherein the radial extension of the channel increases along the axial direction A, or the plate may disclose a first radially increasing portion and a second radially decreasing portion. As disclosed in the general description of the invention, combined or alternatively, the radial extension of the channel may vary along the circumferential direction C.

[0044] Figure 4 This allows for the disclosure of how the damping device 28 can be attached to the burner liner. Specifically, Figure 4 The present application discloses a sequential liner 26 in the form of a tubular main body and a damping device 28 arranged annularly around a portion of the liner 26. Figure 5 It was made public. Figure 4 An enlarged view of a portion of the lining 26. According to this example, the damping volume 29, arranged annularly around a portion of the lining 26, is divided into multiple sub-volumes by a plurality of axial separators. In this case, the radial extension of the channel varies along the circumferential direction C. Figure 5 The purge air port 34 for purge air entering the damping volume 29 is also disclosed.

[0045] Although the invention has been explained with respect to the preferred embodiments described above, it should be understood that many other possible modifications and variations can be made without departing from the scope of the invention. Therefore, it is contemplated that the appended claims or multiple claims will cover modifications and variations that fall within the true scope of the invention.

Claims

1. A gas turbine for use in electrical equipment; said gas turbine (1) having a shaft (9) and comprising: - Compressor section (2) used to compress ambient air, - A burner (4) for mixing and burning compressed air with at least one fuel; the burner (4) includes at least one liner (7, 26) defining a combustion chamber (6, 21, 23) having an axial direction (A) and a circumferential direction (C); - At least one turbine section (3) for expanding the hot gas flow leaving the burner (4) and doing work on the rotor (8); - At least one damping device (28) disposed outside the combustion chambers (6, 21, 23) and comprising a damping volume (29) and a perforated plate (30), the perforated plate (30) being configured to fluidly connect the combustion chambers (6, 21, 23) to the damping volume (29) to dampen pressure fluctuations generated within the combustion chambers (6, 21, 23); Its features The perforated plate (30) is inclined such that the radial thickness of the perforated plate (30) varies along the axial burner direction (A) and / or along the circumferential burner direction (C); The perforated plate (30) includes an inner surface (31), an outer surface (32), and a plurality of channels (33) extending from the inner surface (31) to the outer surface (32); wherein the inner surface (31) is arranged on the outer surface of the burner liner; the burner liner includes a plurality of holes at the channels (33) for fluidly connecting the combustion chamber (6, 21, 23) to the damping volume (29); The inner surface (31) is flat and parallel to the axial burner direction (A), and the outer surface (32) is inclined relative to the axial burner direction (A) and / or along the circumferential burner direction (C), such that the radial extension of the channel (33) varies along the axial burner direction (A) and / or along the circumferential burner direction (C).

2. The gas turbine of claim 1, wherein, At least the perforated plate (30) is achieved by an additive manufacturing process.

3. The gas turbine as claimed in claim 1, wherein, The radial extension of the channel (33) decreases along the direction of the hot gas flow (M).

4. The gas turbine as claimed in claim 1, wherein, The radial extension of the channel (33) increases along the direction of the hot gas flow (M).

5. The gas turbine as claimed in claim 1, wherein, In the first portion of the perforated plate (30), the radial extension of the channel (33) decreases along the axial burner direction (A), and in the second portion of the perforated plate (30), the radial extension of the channel (33) increases along the axial burner direction (A).

6. The gas turbine as claimed in claim 1, 3, 4, or 5, wherein, The radial extension of the channel (33) varies along the circumferential burner direction (C).

7. The gas turbine as claimed in claim 1, 3, 4, or 5, wherein, The radial extension of the channel (33) is constant along the circumferential burner direction (C).

8. The gas turbine as claimed in claim 1, wherein, The damping volume (29) extends radially at a constant rate along the axial burner direction (A).

9. The gas turbine as claimed in claim 1, wherein, The damping device (28) includes a purge port for allowing purge air to enter the damping volume (29).

10. The gas turbine as claimed in claim 1, wherein, The burner is a canister burner; the damping device (28) is annular around a portion of the burner liner.

11. The gas turbine of claim 10, wherein, The canister burner is configured to perform two combustion stages in series and includes an upstream liner and a downstream liner; the damping device (28) is annular around a portion of the downstream liner.

12. The gas turbine as claimed in claim 9 or 10, wherein, The damping volume (29) comprises multiple sub-volumes separated by multiple axial partition walls.

13. The gas turbine as claimed in claim 2, wherein, At least the perforated plate (30) is manufactured using a printing process.

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